Analysis :: Joining Multiple Dimensions In MDX

I'm new to MDX, and most of the time I customize existing queries rather than writing new ones. I currently have a MDX query like this

SELECT 
[Measures].[Fees Billed]
                  on 0,
except([Age].[Day Buckets].members, {[Age].[Day Buckets].[All], [Age].[Day Buckets].&[Unknown]})
  on 1
FROM 
     MyCube
WHERE ([Fiscal Period].[Fiscal Year].&[2015], [Customer].[City].&[Auckland] )

Which brings the fees billed by age buckets where the customer's city is Auckland. I also have another dimension called [Sales Agent] with a member [City] in it, and there is a member in [Customer] called [Customer].[Sales Agent]

I am trying to retrieve the same information where the customer's sales agent's city is Auckland rather than the customer's city.

If it is SQL, I will join Customer and SalesAgent on Customer.SalesAgentUno = SalesAgent.SalesAgentUno and bring in the desired data. Any way in MDX to do this?